Field
The present invention relates to pressure regulators. More particularly, the present invention relates to pressure regulators useful for regulating the hydraulic pressure in a fluid circuit configured to open and close a blowout preventer surrounding an opening in fluid communication with a bore hole used for the drilling for, and production of, hydrocarbons from subsurface formations, as well as for other hydraulic applications, wherein the dampening of the response of the regulator to a change in the regulated pressure in the fluid circuit is user selective.
Description of the Related Art
Hydraulic circuits used to open and close blowout preventers, or other fluid operated devices such as valves in a hydraulic control circuit, typically must maintain a desired or “set point” operating pressure available for the operation of the fluid operated device. The set point pressure is typically maintained with a tolerance on the order of 1 to 10% of the center of the set point range. The operation of the blowout preventer, as well as of the hydraulic components in a hydraulic control circuit, can cause undesirable changes in the pressure of the fluid in the hydraulic circuit which is supplied to the hydraulically operated component(s), leading to undesirable performance thereof. For example, where the fluid of the hydraulic circuit is used to close the rams of a blowout preventer, a sudden drop in fluid pressure can occur as the rams begin moving to the closed position.
Pressure regulators are placed in a hydraulic circuit between a source of high pressure fluid at or above the set point pressure of the hydraulic circuit and a hydraulically operated component, to selectively fluidly connect the pressure regulated fluid which operates a hydraulically operated component with the high pressure fluid, when the regulated fluid pressure in the hydraulic fluid circuit is too low. Additionally, the pressure regulator is simultaneously fluidly located between the pressure regulated hydraulic circuit fluid and a vent maintained at a pressure below the set point pressure of the hydraulic fluid circuit, and the pressure regulator selectively places the regulated fluid in communication with the vent when the pressure of the regulated fluid exceeds the desired set point.
In current pressure regulators, the regulator body typically includes a supply port and a vent passage leading inwardly thereof, a regulated pressure outlet leading inwardly thereof, and a seal carrier plate, configured as a generally rectangular gate or plate, having openings therein which are located within the seal carrier plate at positions such that, as the seal carrier plate moves within the body of the regulator, the openings are selectively aligned with none of the supply or vent passages, with the vent passage and not the supply passage if the regulated pressure exceeds the pressure set point value, and with the supply passage and not the vent passage when the supply pressure falls below the pressure set point value. The seal carrier plate is biased, by an external spring structure, to position the seal carrier plate, when the regulated pressure is within the pressure set point upper and lower tolerance limits, so that both the supply passage and vent passage, and the fluids therein, are isolated from the pressure regulated fluid. The spring force is balanced by the regulated pressure bearing on a piston structure located between the regulated pressure volume of the regulator and the spring structure, with the piston structure connected through a stem extending therefrom to the seal carrier plate. When the regulated pressure exceeds the set point pressure, the force of the piston against the springs is increased, tending to move the seal carrier plate in the direction of the springs and thereby compress the springs, and simultaneously moving the vent opening in the spring plate into at least a partial overlapping position with respect to the lower pressure vent passage, thereby allowing the higher pressure fluid in the regulated fluid volume to communicate with the lower pressure region through the vent passage, thereby reducing the pressure in the regulated fluid back to within the set point range limits. When this occurs, the pressure on the piston is reduced, and the piston and seal carrier plate connected thereto move back to the steady state condition by the force of the spring, wherein both the vent and supply passages are isolated from the regulated fluid passage. This occurs because the spring force acting to push the piston inwardly of the regulator body is selected to balance with the force on the piston caused by the regulated fluid within the set point range limits acting on the surface area of the piston. If the fluid pressure of the regulated fluid in the regulator falls, the pressure thereof on the piston is reduced, the spring force and pressure force on the piston no longer are balanced, and the springs urge the seal carrier plate in the direction of the regulator body, thereby positioning a supply opening in the seal carrier plate to become at least partially aligned with the supply passage, wherein the higher supply pressure fluid communicates with the regulated fluid and boosts the regulated pressure back to within the set point range limits, which causes the piston to compress the springs and move the seal carrier plate back to the steady state, balanced, condition.
One issue which can occur during the use of the regulator where the regulated pressure spikes upwardly or downwardly, is cycling of the seal carrier plate, also known as chatter. This occurs when the seal carrier plate moves rapidly between the condition where the vent is in communication with the regulated fluid or the supply passage is in communication with the regulated fluid, and then the seal carrier plate moves to its steady state position, but overshoots that position, resulting in the seal carrier plate moving rapidly back and forth and sequentially, and repeatedly, exposing the regulated fluid to the vent and the supply pressures, or where the disconnection of the vent or supply to the regulated fluid occurs too rapidly, pressure waves will travel in the hydraulic circuit. For example, where a vented state of the regulator is rapidly terminated, a pressure spike can occur in the regulated fluid, resulting in another venting event, followed by another spike, etc. The same can occur in the event of rapidly closing off the high pressure supply passage from the regulated fluid passage. In an attempt to ameliorate these effects, the seal carrier plate typically has a second piston structure aligned with the piston which is in communication with the regulator fluid and pressure, in a cavity in the regulator body on the side of the seal carrier plate opposite to the first piston. A feedback line or pressure relief line connects to this cavity. As the seal carrier plate moves in response to variations on the regulated pressure, the movement of the second piston draws fluid into, or exhausts fluid from, the cavity within which the piston is received, tending to dampen or reduce the speed of movement of the seal carrier plate, resulting in slower opening and closing of communication of one of the vent or supply passages with the regulated fluid passage, and lower likelihood of seal carrier plate overshoot. However, this dampening is not variable, in that the diameters of the fluid passages feeding the dampening cavity, and thus the fluid restriction on fluid in the fluid circuit passages feeding the dampening cavity, is fixed, and thus if a different dampening characteristic is desired, a different regulator having a different dampening characteristic must be used.